/*
 *                               POK header
 *
 * The following file is a part of the POK project. Any modification should
 * be made according to the POK licence. You CANNOT use this file or a part
 * of a file for your own project.
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2021 POK team
 */

/* @(#)e_sinh.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/* __ieee754_sinh(x)
 * Method :
 * mathematically sinh(x) if defined to be (exp(x)-exp(-x))/2
 *	1. Replace x by |x| (sinh(-x) = -sinh(x)).
 *	2.
 *		                                    E + E/(E+1)
 *	    0        <= x <= 22     :  sinh(x) := --------------, E=expm1(x)
 *			       			        2
 *
 *	    22       <= x <= lnovft :  sinh(x) := exp(x)/2
 *	    lnovft   <= x <= ln2ovft:  sinh(x) := exp(x/2)/2 * exp(x/2)
 *	    ln2ovft  <  x	    :  sinh(x) := x*shuge (overflow)
 *
 * Special cases:
 *	sinh(x) is |x| if x is +INF, -INF, or NaN.
 *	only sinh(0)=0 is exact for finite x.
 */

#ifdef POK_NEEDS_LIBMATH

#include "math_private.h"
#include <libm.h>

static const double one = 1.0, shuge = 1.0e307;

double __ieee754_sinh(double x) {
  double t, w, h;
  int32_t ix, jx;
  uint32_t lx;

  /* High word of |x|. */
  GET_HIGH_WORD(jx, x);
  ix = jx & 0x7fffffff;

  /* x is INF or NaN */
  if (ix >= 0x7ff00000)
    return x + x;

  h = 0.5;
  if (jx < 0)
    h = -h;
  /* |x| in [0,22], return sign(x)*0.5*(E+E/(E+1))) */
  if (ix < 0x40360000) { /* |x|<22 */
    if (ix < 0x3e300000) /* |x|<2**-28 */
      if (shuge + x > one)
        return x; /* sinh(tiny) = tiny with inexact */
    t = expm1(fabs(x));
    if (ix < 0x3ff00000)
      return h * (2.0 * t - t * t / (t + one));
    return h * (t + t / (t + one));
  }

  /* |x| in [22, log(maxdouble)] return 0.5*exp(|x|) */
  if (ix < 0x40862E42)
    return h * __ieee754_exp(fabs(x));

  /* |x| in [log(maxdouble), overflowthresold] */
  GET_LOW_WORD(lx, x);
  if (ix < 0x408633CE || ((ix == 0x408633ce) && (lx <= (uint32_t)0x8fb9f87d))) {
    w = __ieee754_exp(0.5 * fabs(x));
    t = h * w;
    return t * w;
  }

  /* |x| > overflowthresold, sinh(x) overflow */
  return x * shuge;
}
#endif
